This initiative was launched at the NIAPP Workshop "Neutrinos in Astro and Particle Physics" held at TU Munich on July 14-25 2014. Part of this workshop was devoted to review the evidence for and against - keV scale - sterile neutrino as a possible warm/cold Dark Matter candidate. At the cross road of particle physics, astrophysics, and cosmology, the observational constraints, the production mechanisms in the early Universe, and the experimental perspectives have been discussed. As an outcome of the workshop the participants proposed to gather the current status of this field in a white paper.
Editorial Committee: Marco Drewes, Thierry Lasserre, Alexander Merle, Susanne Mertens
Executive Summary
I - Neutrinos in the Standard Model of Particle Physics and Beyond
(Section Editors: Carlo Giunti and André de Gouvea)
1. Current status of Neutrino Masses and Oscillations
2. Open questions in Neutrino Physics
2.1 Neutrino Masses
2.2 Neutrino Nature, Dirac or Majorana
2.3 Neutrino Mass Hierarchy
2.4 Neutrino CP violation
2.5 Additional neutrino states
3. Sterile Neutrinos
3.1 eV-scale
3.2 keV-scale
3.3 GeV, TeV, and >>TeV scales
II - Neutrinos in The Standard Model of Cosmology and Beyond
(Section Editors: Julien Lesgourgues and Alessandro Mirizzi)
1. Cosmological Concordance Model (J. Hamann, G. Mangano)
2. Active neutrinos in Cosmology (J. Lesgourgues, S. Pastor)
3. Sterile neutrinos in Cosmology
3.1 eV-scale (M. Archidiacono, N. Saviano)
3.2 KeV-scale (A. Boiarskyi, O. Ruchayskiy)
3.3 Mev-scale (S. Pascoli)
3.4 GeV-TeV (A. Ibarra)
3.5 Leptogenesis (P. Di Bari)
III - Dark Matter at Galactic Scales: Observational Constraints & Simulations (Astro)
(Section Editors: Aurel Schneider, Francesco Shankar and Oleg Ruchayskiy)
1. The Matter Power Spectrum & Status of Galactic-scale Structure Simulations
2. The too-big-to-fail issue
3. The Galactic Halo Cusps issue
4. The Missing Satellite issue
5. Proposed solution: CDM / WDM / Mixed-DM
IV - Established constraints on keV Neutrino Dark Matter
(Section Editor: George Fuller, to be written in close collaboration with Section V)
1. Pauli blocking (D. Gorbunov)
2. Lyman alpha (M. Vie)
3. X-rays - Hint for keV neutrino X-ray signal (O. Ruchaiskiy and A. Neronov)
4. Laboratory contraints on keV neutrinos (S. Mertens)
V - Constraining keV Neutrino Production Mechanisms
(Section Editors: Marco Drewes, Fedor Bezrukov and G. Fuller)
1. Dodelson-Widrow (G. Fuller, M. Drewes)
2. Shi-Fuller (G. Fuller, M. Drewes)
3. Scalar Decay (I. Tkachev)
4. Entropy Dilution
5. Discussion
VI - keV Neutrino Theory and Model Building (Particle Physics)
(Section Editors: Alexander Merle and Viviana Niro)
1. General Principles of keV Neutrino Model Building (Alexander Merle and Viviana Niro)
2. Models based on Suppression Mechanisms:
2.1 Split seesaw + extensions (A. Kusenko, R. Takahash)
2.2 Froggatt-Nielsen + variants (A. Merle, V. Niro)
2.3 Minimal radiative inverse seesaw (A. Pilaftsis, B. Dev)
2.4 Further models based on loop suppressions (D. Borah, R. Adhikari)
3. Models based on Symmetry Breaking:
3.1 L_e-L_mu-L_tau (A. Merle, V. Niro)
3.2 A_4 (A. Merle)
3.3 Q_6 (T. Araki)
4. Models based on other principles:
4.1 Extended seesaw (J. Heeck)
4.2 Dynamical mass generation/composite neutrinos (D. Robinson, Y. Tsai)
4.3 331-models (A. Gomes Dias, N. Anh Ky)
4.4 Geometric torsions/string theory (N. Mavromatos, A. Pilaftsis)
VII - Current & Future keV Neutrino Search with Astrophysical Experiments
(Section Editors: Steen Hansen and Alexei Boyarsky)
1. X-ray telescopes
2. Lyman alpha
3. Pulsar kick
4. Supernovae
VIII - Current & Future keV Neutrino Search with Laboratory Experiments
(Section Editors: Susanne Mertens and Loredana Gastaldo)
1. Effect of keV sterile neutrinos on beta decay spectra
1.1 The case of H-3
- Troitsk
- KATRIN (S. Mertens, T. Lasserre)
- Project8 (B. Monreal)
- Ptolemy (C. Tully)
- Full kinematic reconstruction
1.2 The case of Re-187
- MANU (F. Gatti, M. Galeazzi)
- MIBETA (A. Nucciotti)
- MARE (F. Gatti, A. Nucciotti)
IX - Discussion - Pro and Cons for keV Neutrino as Dark Matter and Perspectives